In the medical and non-destructive examination fields, a radiation imaging device, which generates an image to be examined by oppositely disposing a radiation source and a detector in which many detection elements for detecting a radiation are arranged across an object to be examined and detecting a radiation transmitted through the object to be examined with the detector, is used widely. Particularly in the medical field, a radiation imaging device, which acquires a tomographic image of an object to be examined by rotating the radiation source and the detector around the object to be examined and using projection data scanned at various angles during the rotation, is used, and the representative example is an X-ray CT apparatus. In such a radiation imaging device, a wide range can be scanned in one rotation because a detector is provided with multiple rows in the rotation axis direction, which can shorten the scanning time.
On the other hand, as the number of detection elements increases rapidly due to the multi-row configuration of the detector, a possibility that broken detection elements (hereinafter, referred to as defective elements) can be generated is increases. The defective elements are generated due to a breakdown, manufacturing failure, and the like of a photodiode changing light to an electric signal and a reading circuit, and there are cases where the defective elements exist immediately after the device was manufactured and where the defective elements are generated as the device is used. If a detector in which the defective elements were generated is used in a CT device as is, artifacts are generated in a reconstructed image, which results in a problem of hindering diagnosis.
A sure method to remove the influence of the defective elements is to replace the defective elements and the detector therewith with the new ones. However, in addition to the cost to prepare the new detector, it requires many work steps and much of cost and time to replace a detector, to prepare detectors for replacement in advance, and the like. Also, if the defective elements are found in a clinical site, it takes much time to solve the problem, which can cause a dead time.
The other method is to perform image correction. As described in the patent literature 1, for example, this method is to set an average value of the surrounding normal elements as a correction value of a defective element for an acquired image, which can be performed easily, inexpensively, as well as immediately and is very effective. Particularly, if the defective elements are found in a clinical site, this is very effective because a dead time of the device can be reduced to the minimum.